<?php 
header('Content-type:text/html;charset=utf-8');
class Hd{
	private $app = '应用';
	private $link = '连接';
	
	//外部unset删除私有属性的时候，会自动触发__unset
	//然后会把属性的名称传入
	public function __unset($name){
		unset($this->$name);
	}
	//检测属性是否存在
	public function hdIsset($name){
		var_dump(isset($this->$name));
	}
}
$h = new Hd;
//在外部删除私有属性
unset($h->app);
$h->hdIsset('app');


 ?>